Magnetic memory

ABSTRACT

According to one embodiment, the magnetic memory includes a structure including a first magnetic layer and a conductive layer, a second magnetic layer, an intermediate layer, a third magnetic layer, and a fourth magnetic layer. The first magnetic layer is provided between the second magnetic layer and the conductive layer. The intermediate layer is provided between the second magnetic layer and the first magnetic layer. The third magnetic layer is provided between a second electrode and the intermediate layer. The fourth magnetic layer is provided between a first electrode and the intermediate layer. Further, the magnetic memory includes a first conductive-type first semiconductor layer electrically connected with the first electrode, a first conductive-type second semiconductor layer electrically connected with the second magnetic layer, and a second conductive-type third semiconductor layer electrically connected with the first semiconductor layer and the second semiconductor layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2016-144743 filed on Jul. 22, 2016, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments describe herein relate generally to a magnetic memory.

BACKGROUND

Recently a three terminal magnetic random access memory (MRAM; MagneticRandom Access Memory) using torque which is originally caused byspin-orbit interaction has been proposed. In magnetic memories includingsuch MRAM, improvement of the degree of integration (i.e. highintegration) has been desired.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view illustrating a magnetic memoryaccording to a first embodiment.

FIG. 2 is a schematic view illustrating characteristics of a part of themagnetic memory according to the first embodiment.

FIG. 3 is a schematic view to explain an operation of the magneticmemory according to the first embodiment.

FIG. 4 is a schematic view to explain an operation of the magneticmemory according to the first embodiment.

FIG. 5 is a schematic view to explain an operation of the magneticmemory according to the first embodiment.

FIG. 6 is a schematic sectional view illustrating a magnetic memoryaccording to a second embodiment.

FIG. 7 is a schematic view to explain an operation of the magneticmemory according to the second embodiment.

FIG. 8 is a schematic view to explain an operation of the magneticmemory according to the second embodiment.

FIG. 9 is a schematic view to explain an operation of the magneticmemory according to the second embodiment.

FIG. 10 is a schematic sectional view illustrating a magnetic memoryaccording to a first modification of the second embodiment.

FIG. 11 is a schematic sectional view illustrating a magnetic memoryaccording to a second modification of the second embodiment.

DESCRIPTION OF EMBODIMENTS

According to one embodiment of the present invention, a magnetic memoryincludes a structure including a first magnetic layer and a conductivelayer, a second magnetic layer, an intermediate layer, a third magneticlayer, and a fourth magnetic layer is provided. The first magnetic layeris provided between the second magnetic layer and the conductive layer.The intermediate layer is provided between the second magnetic layer andthe first magnetic layer. The third magnetic layer is provided between asecond electrode and the intermediate layer. The fourth magnetic layeris provided between a first electrode and the intermediate layer. Themagnetic memory includes a first semiconductor layer having a firstconductive-type electrically connected with the first electrode, asecond semiconductor layer having a first conductive-type electricallyconnected with the second magnetic layer, and a third semiconductorlayer having a second conductive-type electrically connected with thefirst semiconductor layer and the second semiconductor layer.

Hereinafter, embodiments of the present invention will be described withreference to the drawings.

Note that the drawings are schematically and conceptually illustrated.Relationship between the thickness and the width of portions, a ratio ofsizes between the portions, and the like are not necessarily the same asthose in reality. Further, dimensions and ratios may be different fromeach other depending on the drawings even if these drawings illustratethe same portion.

Note that, in the specification and the drawings of the presentapplication, an element similar to that described in relation to apreviously described drawing is denoted with the same reference sign anddetailed description is appropriately omitted.

First Embodiment

FIG. 1 is a schematic sectional view illustrating a magnetic memoryaccording to a first embodiment.

As illustrated in FIG. 1, a magnetic memory 100 according to the firstembodiment includes a structure 1. The structure 1 includes a firstmagnetic layer 2 and a conductive layer 3. A first electrode 4 a isprovided on a first portion 1 a of the structure 1. A second electrode 4b is provided on a second portion 1 b of the structure 1. The secondportion 1 b is distant from the first portion 1 a.

In the example of FIG. 1, the first portion 1 a is on the first magneticlayer 2. However, in the present embodiment, the first portion 1 a maybe on the conductive layer 3, or may be on the first magnetic layer 2and the conductive layer 3. The second portion 1 b also may be on theconductive layer 3, or may be on the first magnetic layer 2 and theconductive layer 3. The conductive layer 3 is nonmagnetic. Theconductive layer 3 includes a conductor having large spin-orbitinteraction, for example. Examples of such conductor may includetantalum (Ta) and platinum (Pt).

In the present specification, one direction is defined as an Xdirection. One direction vertical to the X direction is defined as a Ydirection. A direction perpendicular to the X direction and the Ydirection is defined as a Z direction.

The magnetic memory 100 is formed on, for example, a semiconductorsubstrate. For example, a main surface of the semiconductor substrate isan XY plane. In FIG. 1, the semiconductor substrate is omitted and notillustrated.

An intermediate layer (insulating layer) 5 is provided on the firstmagnetic layer 2 of the structure 1. The first magnetic layer 2 includesa third portion 1 c between the first portion 1 a and the second portion1 b.

In the present embodiment, the intermediate layer (insulating layer) 5is provided on the third portion 1 c of the first magnetic layer 2. Asecond magnetic layer 6 is provided on the intermediate layer(insulating layer) 5. The intermediate layer (insulating layer) 5 issandwiched by the first magnetic layer 2 and the second magnetic layer6, and is arranged therebetween. The first magnetic layer 2, theintermediate layer (insulating layer) 5, and the second magnetic layer 6form magnetic tunnel junction (MTJ).

A memory cell MC of the magnetic memory 100 includes the first magneticlayer 2, the intermediate layer (insulating layer) 5, and the secondmagnetic layer 6. Such memory cell MC is, for example, an MTJ storageelement.

The second magnetic layer 6 is a reference layer. The direction ofmagnetization of the reference layer (second magnetic layer 6) is fixed(or pinned) to one of “upward” and “downward” directions, for example.In the present embodiment, the direction of magnetization of thereference layer (second magnetic layer 6) is fixed (or pinned) to theupward direction. In the example of FIG. 1, the direction ofmagnetization goes along the Z direction. In the embodiment, thedirection of magnetization may intersect with the Z direction and isarbitrary. Description will be given, where the direction ofmagnetization is “upward” or “downward”, for convenience.

The first magnetic layer 2 is a magnetic recording layer. A direction ofmagnetization M of the magnetic recording layer (first magnetic layer 2)is variable to either one of the “upward” direction and the “downward”direction. FIG. 1 illustrates a case in which the direction ofmagnetization M is the “upward” direction. A state in which thedirection of magnetization M of the magnetic recording layer (firstmagnetic layer 2) is the “upward direction” and the direction ofmagnetization of the reference layer (second magnetic layer 6) is the“upward” direction is a parallel state. In the parallel state, aresistance value of the MTJ is low.

On the other hand, a state in which the direction of magnetization M ofthe magnetic recording layer (first magnetic layer 2) is the “downward”direction, and the direction of magnetization of the reference layer(second magnetic layer 6) is the “upward” direction is an antiparallelstate. In the antiparallel state, the resistance value of the MTJ ishigh. Information (data) is recorded in the memory cell MC according theresistance value of the MTJ.

A third magnetic layer 7 a and a fourth magnetic layer 7 b are providedin contact with the first magnetic layer 2 on the first magnetic layer 2side of the structure 1. In the present embodiment, the third magneticlayer 7 a is provided between the second electrode 4 b and theintermediate layer (insulating layer) 5 in contact with the firstmagnetic layer 2. Further, the fourth magnetic layer 7 b is providedbetween the first electrode 4 a and the intermediate layer (insulatinglayer) 5 in contact with the first magnetic layer 2.

That is, the second electrode 4 b, the third magnetic layer 7 a, theintermediate layer (insulating layer) 5, the fourth magnetic layer 7 b,and the first electrode 4 a are lined up in a first direction (here, adirection along an X axis).

The third magnetic layer 7 a and the fourth magnetic layer 7 b areantiferromagnetic or ferromagnetic. The directions of magnetization ofthe third magnetic layer 7 a and the fourth magnetic layer 7 b are fixed(or pinned).

In the present embodiment, the directions of the magnetization of thethird magnetic layer 7 a and the fourth magnetic layer 7 b go along theX direction. The third magnetic layer 7 a and the fourth magnetic layer7 b are in contact with the first magnetic layer (magnetic recordinglayer) 2, and are exchange coupled.

In a case where the third magnetic layer 7 a and the fourth magneticlayer 7 b are antiferromagnetic, an effect (called exchange bias) todirect the magnetization of the first magnetic layer (magnetic recordinglayer) 2 to a direction of magnetization along the X direction, ofsurfaces of the third magnetic layer 7 a and the fourth magnetic layer 7b, the surfaces being in contact with the first magnetic layer (magneticrecording layer) 2, is caused. A similar effect is caused even in a casewhere the third magnetic layer 7 a and the fourth magnetic layer 7 b areferromagnetic.

However, antiferromagnetism is desirable because the third magneticlayer 7 a and the fourth magnetic layer 7 b become strong againstdisturbance due to an external magnetic field. The exchange bias is usedto reverse the direction of magnetization of the first magnetic layer 2to a determined direction in writing information.

The third magnetic layer 7 a and the fourth magnetic layer 7 b determinea direction to be reversed to change the parallel state to theantiparallel state when a current is caused to flow in the firstmagnetic layer (magnetic recording layer 2) from the right to the lefton FIG. 1 along the X direction.

When a current flows in the conductive layer 3, a spin current occurs inthe conductive layer 3. When the spin current occurs in the conductivelayer 3, a spin is injected from the conductive layer 3 to the firstmagnetic layer (magnetic recording layer) 2. The direction ofmagnetization M of the first magnetic layer (magnetic recording layer) 2is determined according to whether the direction of the spin injectedfrom the conductive layer 3 is the “upward” or “downward” direction. Thedirection of the spin injected from the conductive layer 3 can bedetermined according to the direction of the current flowing in theconductive layer 3. In writing information, the magnetic memory 100injects the spin from the conductive layer 3 to the first magnetic layer(magnetic recording layer) 2. Such a writing method is, for example, aspin injection method.

The first electrode 4 a is connected with the second electrode 4 bthrough a parallel circuit 110. The parallel circuit 110 includes afirst resistor portion r1 by the conductive layer 3 and a secondresistor portion r2 by the first magnetic layer 2. A resistance value ofthe first resistor portion r1 is lower than a resistance value of thesecond resistor portion r2.

The magnetic memory 100 includes a circuit element 120. The circuitelement 120 includes a first semiconductor layer 8 having a firstconductive-type, a second semiconductor layer 9 having a firstconductive-type, and a third semiconductor layer 10 having a secondconductive-type. The first semiconductor layer 8 is electricallyconnected with the first electrode 4 a. The second semiconductor layer 9is electrically connected with the second magnetic layer 6. The thirdsemiconductor layer 10 is electrically connected with the firstsemiconductor layer 8 and the second semiconductor layer 9.

In the present embodiment, the first semiconductor layer 8 and thesecond semiconductor layer 9 are p-type, and the third semiconductorlayer 10 is n-type, for example. The first semiconductor layer 8 and thesecond semiconductor layer 9 are anodes of diodes. The thirdsemiconductor layers 10 are cathodes of the diodes. The circuit element120 includes diodes D1 and D2. The cathode of the diode D1 is connectedwith the cathode of the diode D2. In the present embodiment, thecathodes of the diodes D1 and D2 are connected. Instead, the anodes ofthe diodes D1 and D2 could be connected. The diodes D1 and D2 are, forexample, a Zener diode.

The magnetic memory 100 includes first wiring 130 a, second wiring 1 30b, a first external terminal 140 a, and a second external terminal 140b. The first external terminal 140 a is electrically connected with thefirst wiring 130 a. The first wiring 130 a is electrically connectedwith the second magnetic layer 6 and the second semiconductor layer 9.The second external terminal 140 b is electrically connected with thesecond wiring 130 b. The second wiring 130 b is electrically connectedwith the second electrode 4 b. The first external terminal 140 a and thesecond external terminal 140 b are terminals connectable with anexternal circuit (not illustrated) outside the magnetic memory 100.

An example of the external circuits includes a circuit that includes acontrol device that controls information write and information readto/from the magnetic memory 100.

Hereinafter, an example of operations of the magnetic memory 100 will bedescribed.

FIG. 2 is a schematic view illustrating characteristics of a part of themagnetic memory according to the first embodiment.

FIG. 2 illustrates current-voltage characteristics of the circuitelement 120.

As illustrated in FIG. 2, the circuit element 120 has a positivethreshold Vth and a negative threshold −Vth. A voltage provided betweenthe first wiring 130 a and the second wiring 130 b refers to “voltagebetween wirings V”. A current I does not flow in the circuit element 120when the voltage between wirings V falls within a range of “−Vth<V<Vth”and is “V<|Vth|”.

The current I flows in the circuit element 120 from the first wiring 130a to the second wiring 130 b when the voltage between wirings V is“Vth≦V”. The current I flows in the circuit element 120 from the secondwiring 130 b to the first wiring 130 a when the voltage between wiringsV is “V≦−Vth”.

Read Operation

A read operation is performed where a voltage between wirings Vr is setto “Vr<|Vth|”. External terminals to be used are, for example, the firstexternal terminal 140 a and the second external terminal 140 b. In theread operation, a first potential difference is provided to the firstexternal terminal 140 a and the second external terminal 140 b. Thevoltage between wirings Vr is set to “Vr<|Vth|” on the basis of thefirst potential difference.

FIG. 3 is a schematic view to explain an operation of the magneticmemory according to the first embodiment.

FIG. 3 exemplarily illustrates a read operation R/O of the magneticmemory 100.

FIG. 3 illustrates a case in which a positive potential is provided tothe first wiring 130 a, and a voltage lower than that of the firstwiring 130 a, for example, a ground potential (0 V) is provided to thesecond wiring 130 b. The voltage between wirings Vr is “0V≦Vr<Vth”. Inthis case, the current I flows from the first wiring 130 a to the secondwiring 130 b through the memory cell MC. The value of the current I ischanged according to a resistance value of the memory cell MC. The valueof the current I becomes large when the resistance value of the memorycell MC is low, and the value of the current I becomes small when theresistance value of the memory cell MC is high. Whether informationrecorded in the memory cell MC is “1” or “0” is determined on the basisof the magnitude of the value of the current I, for example.

In the magnetic memory 100, voltage drop of the memory cell MC can behigher than the voltage between wirings Vr. In this case, the current Idoes not flow. Whether the information recorded in the memory cell MC is“0” or “1” is determined on the basis of whether the current I flows,for example.

In the example of the read operation R/O illustrated in FIG. 3, thepotential of the second wiring 130 b is lower than the potential of thefirst wiring 130 a. However, the potential of the second wiring 130 bcan be higher than the potential of the first wiring 130 a. In thiscase, the current I flows from the second wiring 130 b to the firstwiring 130 a through the memory cell MC. To be specific, a positivepotential is provided to the second wiring 130 b, and 0 V is provided tothe first wiring 130 a. Alternatively, 0 V is provided to the secondwiring 130 b, and the negative potential is provided to the first wiring130 a. Even in this case, whether the information is “1” or “0” isdetermined on the basis of the magnitude of the value of the current I,or whether the current I flows.

Write Operation

A write operation is performed where a voltage between wirings Vw is setto “Vth≦Vw” or “−Vw≦−Vth” according to information to be written.External terminals to be used are, for example, the first externalterminal 140 a and the second external terminal 140 b. In the writeoperation, a second Potential difference is provided to the firstexternal terminal 140 a and the second external terminal 140 b. Thevoltage between wirings Vw is set to “Vth≦Vw” or “−Vw≦−Vth” on the basisof the second potential difference.

FIG. 4 is a schematic view to explain an operation of the magneticmemory according to the first embodiment.

FIG. 4 exemplarily illustrates a write operation W/O of the magneticmemory 100. FIG. 4 illustrates a case in which the voltage betweenwirings Vw is “Vth≦Vw”.

The state illustrated in FIG. 4 is obtained by, for example, providing apositive potential of the positive threshold Vth or more to the firstwiring 130 a, and providing the ground potential (0 V) to the secondwiring 130 b. The current I flows from the first wiring 130 a to thesecond wiring 130 b through the circuit element 120. In this case, thecurrent I flows in the conductive layer 3 from the first electrode 4 ato the second electrode 4 b. Accordingly, the spin is injected from theconductive layer 3 to the first magnetic layer 2. For example, thedirection of magnetization of the first magnetic layer 2 becomes the“upward” direction, and information corresponding to the parallel stateis written in the memory cell MC.

FIG. 5 is a schematic view to explain an operation of the magneticmemory according to the first embodiment.

FIG. 5 exemplarily illustrates the write operation W/O of the magneticmemory 100. FIG. 5 illustrates a case in which the voltage betweenwirings Vw is “−Vw≦−Vth”.

The state illustrated in FIG. 5 can be obtained by, for example,providing the ground potential (0 V) to the first wiring 130 a, andproviding a positive potential of the positive threshold Vth or more tothe second wiring 130 b. Alternatively, the state illustrated in FIG. 5is obtained by providing the negative potential of the negativethreshold −Vth or less to the first wiring 130 a, and providing theground potential (0 V) to the second wiring 130 b. The current I flowsfrom the second wiring 130 b to the first wiring 130 a through thecircuit element 120.

In this case, the current I flows in the conductive layer 3 from thesecond electrode 4 b to the first electrode 4 a. Accordingly, the spinin a reverse direction to the state illustrated in FIG. 4 is injectedfrom the conductive layer 3 to the first magnetic layer 2. For example,the direction of magnetization of the first magnetic layer 2 becomes the“downward” direction, and information corresponding to the antiparallelstate is written to the memory cell MC.

When the magnetic memory 100 performs the read operation R/O, forexample, the first potential difference is provided to the firstexternal terminal 140 a and the second external terminal 140 b. Themagnetic memory 100 performs the read operation R/O on the basis of thefirst potential difference.

The second potential difference is provided to the first externalterminal 140 a and the second external terminal 140 b when the magneticmemory 100 performs the write operation W/O. The magnetic memory 100performs the write operation W/O on the basis of the second potentialdifference.

Therefore, the magnetic memory 100 may not differently use the externalterminals between in the read operation R/O and in the write operationW/O. Therefore, the number of the external terminals according to thefirst embodiment can be reduced, compared with a magnetic memory 100that differently uses the external terminals between in the readoperation R/O and in the write operation W/O.

At least a part of the third magnetic layer 7 a and the fourth magneticlayer 7 b overlaps with at least a part of an area between the firstportion 1 a and the second portion 1 b in a direction intersecting witha direction connecting the first portion 1 a and the second portion 1 b.Therefore, the magnetic memory 100 can record a plurality of pieces ofinformation in the second magnetic layer 6 between the first portion 1 aand the second portion 1 b of the structure 1.

Further, the first wiring 130 a is provided the potential not only whenthe read operation R/O is performed but also when the write operationW/O is performed. Therefore, in a memory cell array in which the memorycells MC are integrated, wiring for the read operation R/O and wiringfor the write operation W/O may not be separately provided. Therefore,the degree of integration of the memory cell array in the magneticmemory 100 can be improved, compared with a magnetic memory providedwith the wiring for the read operation R/O and the wiring for the writeoperation W/O in the memory cell array.

A higher TMR ratio is required for the memory cell MC. Accordingly,design/manufacturing margin of the magnetic memory 100 is increased. Toobtain the high TMR ratio, a difference between the resistance values isincreased between a high resistance state and a low resistance state.However, if the resistance value in the high resistance state is madetoo high, the current becomes less flowable in the memory cell MC duringthe write operation W/O, and the write characteristics of the memorycell MC are degraded.

Under in the circumstances, the magnetic memory 100 does not allow thecurrent to flow in the memory cell MC during the write operation W/O.Therefore, the resistance value in the high resistance state can beincreased without degrading the write characteristics, compared with acase in which the current flows in the memory cell MC during the writeoperation W/O. Therefore, in the magnetic memory 100, thedesign/manufacturing margin can be increased.

The magnetic memory 100 can write information when the voltage betweenwirings Vw becomes the positive threshold Vth or more, or the negativethreshold −Vth or more, of the circuit element 120, regardless of theresistance value of the memory cell MC. Therefore, the resistance valueof the memory cell MC can be increased to a value with which noconduction is performed with the voltage between wirings Vw provided inthe write operation W/O.

As described above, according to the magnetic memory 100 of the firstembodiment, a magnetic memory that enables improvement of the degree ofintegration can be provided. Further, for example, the number of theexternal terminals can be reduced. Further, for example, thedesign/manufacturing margin can be increased.

Second Embodiment

A second embodiment relates to an example of a case in which themagnetic memory 100 according to the first embodiment is applied to amagnetic domain wall motion memory.

FIG. 6 is a schematic sectional view illustrating a magnetic memoryaccording to the second embodiment.

A magnetic memory 300 according to the second embodiment is an examplein which a third electrode 4 c is further provided to the magneticmemory 100 illustrated in FIG. 1. The third electrode 4 c is provided ona third portion 1 c of a structure 1. Third wiring 130 c is electricallyconnected to the third electrode 4 c. The third wiring 130 c iselectrically connected to a third external terminal 140 c.

The magnetic memory 300 including the third electrode 4 c on thestructure 1 can be used as a magnetic domain wall motion memoryincluding a first magnetic layer 2 as a magnetic recording layer. Amagnetic domain wall 60 is caused in the first magnetic layer 2 to crossthe first magnetic layer 2. In moving the magnetic domain wall 60, afirst shift current Isf1 from a second electrode 4 b to the thirdelectrode 4 c is caused to flow in at least the first magnetic layer 2.Alternatively, a second shift current Isf2 from the third electrode 4 cto the second electrode 4 b is caused to flow in at least the firstmagnetic layer 2. The first shift current Isf1 and the second shiftcurrent Isf2 flow in the first magnetic layer 2, penetrating themagnetic domain wall 60.

In a case where the first shift current Isf1 flows, the magnetic domainwall 60 is shifted, for example, to the right on the sheet surface. In acase where the second shift current Isf2 flows, the magnetic domain wail60 is shifted, for example, to the left on the sheet surface.

Magnetic domains 61 are set to the first magnetic layer 2 by themagnetic domain wall 60, for example. A plurality of the magneticdomains 61 may be provided to the first magnetic layer 2. The directionof magnetization may simply be changed on the right and left of onemagnetic domain wall 60.

In this case, the magnetic domain wall 60 caused in the first magneticlayer 2 is shifted either to the right or left below an intermediatelayer (insulating layer) 5. Accordingly, information “1” or information“0” can be stored.

However, if the magnetic domains 61 divided by the magnetic domain walls60 are set to the first magnetic layer 2, for example, a plurality oftwo or more pieces of information (data) can be recorded in the firstmagnetic layer 2. FIG. 6 illustrates an example in which four magneticdomains 61 a, 61 b, 61 c, and 61 d are set to the first magnetic layer2.

In this case, the four pieces of information can be recorded in thefirst magnetic layer 2.

The magnetic memory 300 is, for example, a magnetic domain wall motionmemory. The magnetic memory 300 includes a read head 62 and a write head63.

The read head 62 includes the first magnetic layer 2, the intermediatelayer (insulating layer) 5, and a second magnetic layer 6. The directionof magnetization of the second magnetic layer 6 is fixed (or pinned)similarly to the first embodiment. In the present embodiment, thedirection is fixed (or pinned) to an “upward” direction.

The write head 63 includes the first magnetic layer 2, a conductivelayer 3, a third magnetic layer 7 a, and a fourth magnetic layer 7 b.The third magnetic layer 7 a and the fourth magnetic layer 7 b provide abias magnetic field for inverting the direction of magnetization of thefirst magnetic layer 2 to the first magnetic layer 2 and the conductivelayer 3.

Hereinafter, an example of a read operation R/O, a shift operation, anda write operation W/O of the magnetic memory 300 will be described.

Read Operation

The read operation R/O is performed where a voltage between wirings Vris set to “Vr<|Vth|”.

FIG. 7 is a schematic view to explain an operation of the magneticmemory according to the second embodiment.

FIG. 7 exemplarily illustrates the read operation R/O of the magneticmemory 300.

As illustrated in FIG. 7, the read operation R/O is similar to that ofthe magnetic memory 100 according to the first embodiment. The voltagebetween wirings Vr is “Vr<|Vth|”. Whether information recorded in themagnetic recording layer (first magnetic layer 2) is “1” or “0” isdetermined according to the magnitude of a value of a current I flowingin the read head 62, for example. Alternatively, whether the informationis “1” or “0” is determined according to whether the current I flows inthe read head 62, for example. External terminals to be used are a firstexternal terminal 140 a and a second external terminal 140 b.

Write Operation

The write operation W/O is performed where a voltage between wirings Vwis set to “Vth≦Vw” or “−Vw≦−Vth” according to information to be written.

FIG. 8 is a schematic view to explain an operation of the magneticmemory according to the second embodiment.

FIG. 8 exemplarily illustrates the write operation W/O of the magneticmemory 300.

As illustrated in FIG. 8, the write operation W/O is similar to that ofthe magnetic memory 100 according to the first embodiment. The voltagebetween wirings Vw is set to be “Vth≦Vw” or “−Vw≦−Vth” according to theinformation to be written. “Vth≦Vw” is a case in which a potential ofthe first wiring 130 a is made higher than a potential of the secondwiring 130 b. “−Vw≦−Vth” is a case in which the potential of the firstwiring 130 a is made lower than the potential of the second wiring 130b. The potential of the second wiring 130 b is fixed to a groundpotential (for example, 0 V), and the potential of the first wiring 130a is set to a positive potential or a negative potential according tothe information to be written.

Alternatively, the potential of the second wiring 130 b and thepotential of the first wiring 130 a are swapped according to theinformation to be written. Accordingly, a spin is injected from theconductive layer 3 to any of the magnetic domains 61 a to 61 d in thewrite head 63, and the direction of magnetization is determined. Thedirection of magnetization is determined according to the direction ofthe current I flowing in the conductive layer 3.

Shift Operation

The shift operation is performed where a voltage between wirings Vsf isset to “Vw<Vsf” or “−Vsf<−Vw” according to the direction into which theinformation is shifted. The voltage between wirings Vsf is a voltagebetween the second wiring 130 b and the third wiring 130 c. The externalterminals to be used are the second external terminal 140 b and thethird external terminal 140 c. For example, in the shift operation, athird potential difference is provided to the second external terminal140 b and the third external terminal 140 c. The voltage between wiringsVsf is set to “Vw<Vsf” or “−Vsf<−Vw” on the basis of the third potentialdifference.

FIG. 9 is a schematic view to explain an operation of the magneticmemory according to the second embodiment.

FIG. 9 exemplarily illustrates the shift operation S/O of the magneticmemory 300. FIG. 9 illustrates a case in which the voltage betweenwirings Vsf is set to “Vw<Vsf”.

“Vw<Vsf” is a case in which a potential of the third wiring 130 c ismade higher than the potential of the second wiring 130 b. “−Vsf<−Vw” isa case in which the potential of the third wiring 130 c is made lowerthan the potential of the second wiring 130 b. In the shift operationS/O, for example, the potential of the second wiring 130 b is set to theground potential (for example, 0 V), and the potential of the thirdwiring 130 c is set to the positive potential or the negative potentialaccording to the direction into which the information is shifted.Alternatively, the potential of the second wiring 130 b and thepotential of the third wiring 130 c are swapped according to thedirection into which the information is shifted.

When “Vw<Vsf”, the first shift current Isf1 flows from the thirdelectrode 4 c to the second electrode 4 b through the first magneticlayer 2 and the conductive layer 3 (see FIG. 9). When the first shiftcurrent Isf1 flows in the first magnetic layer 2, penetrating themagnetic domain wall 60, the magnetic domain wall 60 is shifted from thethird electrode 4 c side to the second electrode 4 b side. The magneticdomains 61 a to 61 d are shifted from the third electrode 4 c to thesecond electrode 4 b.

When “−Vsf<Vw”, the second shift current Isf2 in the reverse directionflows from the second electrode 4 b to the third electrode 4 c throughthe first magnetic layer 2 and the conductive layer 3 (the second shiftcurrent Isf2 is not especially illustrated). When the second shiftcurrent Isf2 flows in the first magnetic layer 2, penetrating themagnetic domain wall 60, the magnetic domain wall 60 is shifted from thesecond electrode 4 b side to the third electrode 4 c side. The magneticdomains 61 a to 61 d are shifted from the second electrode 4 b to thethird electrode 4 c.

The voltages between wirings Vsf and −Vsf are provided, for example, bypulse forms. While the voltages between wirings Vsf and −Vsf areprovided by the pulse forms, the first shift current Isf1 and the secondshift current Isf2 flow. The magnetic domain wall is moved while thefirst shift current Isf1 and the second shift current Isf2 flow. Adistance by which the magnetic domain wall 60 is moved in one pulse is adistance of one of the magnetic domains 61 a to 61 d, for example.However, the distance by which the magnetic domain wall 60 is moved inone pulse is not limited thereto.

FIG. 9 illustrates a case in which the magnetic domain 61 b is in theread head 62 and the write head 63. In a case where the magnetic domain61 c is shifted to the read head 62 and the write head 63 from themagnetic domain 61 b, for example, one pulse of the voltage betweenwirings Vsf is provided. Accordingly, the magnetic domain 61 c isshifted to the read head 62 and the write head 63.

In a case where the magnetic domain 61 a is shifted to the read head 62and the write head 63 from the magnetic domain 61 b, for example, onepulse of the voltage between wirings −Vsf is provided. Accordingly, themagnetic domain 61 a is shifted to the read head 62 and the write head63.

In the shift operation S/O, the magnetic domain in which information tobe read is recorded, of the magnetic domains 61 a to 61 d, is shifted tothe read head 62. Further, the magnetic domain to which the informationis to be written, of the magnetic domains 61 a to 61 d, is shifted tothe write head 63.

During the shift operation S/O, the first shift current Isf1 and thesecond shift current Isf2 flow not only in the first magnetic layer 2but also in the conductive layer 3. The flowing of the current in theconductive layer 3 is similar to the write operation W/O. A differentpoint is that whether the magnetic domain wall 60 is moved or stopped inthe first magnetic layer 2. If the magnetic domain wall 60 is moved,spin injection to the first magnetic layer 2 is suppressed even if acurrent flows in the conductive layer 3.

In other words, during the write operation W/O, the magnetic domain wall60 is stopped. Accordingly, the spin injection to the first magneticlayer 2 is facilitated. During the shift operation S/O, the magneticdomain wall 60 is moved.

Accordingly, the spin injection to the first magnetic layer 2 issuppressed. Whether the magnetic domain wall 60 remains stopped or ismoved can be controlled by the magnitude of the current to flow in thefirst magnetic layer 2.

According to the magnetic memory 300 according to the second embodiment,a magnetic domain wall motion memory (hereinafter, referred to as a spininjection magnetic domain wall motion memory) in which a writing methodfor information is a spin injection method) is provided.

In the magnetic memory 300, the read operation R/O is performed on thebasis of a first potential difference provided to the first externalterminal 140 a and the second external terminal 140 b. The writeoperation W/O is performed on the basis of a second potential differenceprovided to the first external terminal 140 a and the second externalterminal 140 b. Therefore, it is not necessary to use the externalterminals differently between in the read operation R/O and in the writeoperation W/O. Therefore, the number of the external terminals of thespin injection magnetic domain wall motion magnetic memory can bereduced.

Similarly to the first embodiment, a special wiring for write is notnecessary in a memory cell array in the magnetic memory 300. Therefore,in the spin injection magnetic domain wall motion memory, the degree ofintegration of the memory cell array can be improved.

The magnetic memory 300 does not allow a current to flow in the readhead 62 during the write operation W/O.

Therefore, a resistance value of an MTJ element of the read head 62 canbe increased without decreasing write characteristics. Therefore, in aspin injection magnetic domain wall motion memory, itsdesign/manufacturing margin can be increased.

In another example of the present embodiment, the fourth magnetic layer7 b can be omitted. Then, the intermediate layer (insulating layer) 5,the first electrode 4 a, the second electrode 4 b, and the thirdmagnetic layer 7 a are lined up in the first direction (the directionalong the X axis).

Hereinafter, modifications of the second embodiment will be described.

Second Embodiment: First Modification

FIG. 10 is a schematic sectional view illustrating a magnetic memoryaccording to a first modification of the second embodiment.

As illustrated in FIG. 10, a magnetic memory 301 according to a firstmodification is an example in which a read head 62 is provided in anarea between a first electrode 4 a and a third electrode 4 c. Anintermediate layer (insulating layer) 5 is provided on a fourth portion1 d of a structure 1, of the structure 1. The fourth portion 1 d isbetween the first electrode 4 a and the third electrode 4 c.

As described above, the read head 62 is not necessarily provided in anarea between the first electrode 4 a and a second electrode 4 b.

Second Embodiment: Second Modification

FIG. 11 is a schematic sectional view illustrating a magnetic memoryaccording to a second modification of the second embodiment.

As illustrated in FIG. 11, a magnetic memory 302 according to the secondmodification has a read head 62 provided in an area between a firstelectrode 4 a and a third electrode 4 c, similarly to the magneticmemory 301 according to the first modification.

A different point is that an area between the read head 62 and the firstelectrode 4 a is a storage area 64. The storage area 64 is an area inwhich a plurality of magnetic domains 61 a to 61 d of is shifted by ashift operation S/O. In this way, the magnetic memory 302 includes thestorage area 64. The storage area 64 is provided between the read head62 and the first electrode 4 a.

Further, in the magnetic memory 302, a write head 63 is provided in aportion distant from the storage area 64. Therefore, during a readoperation R/O, the plurality of magnetic domains 61 a to 61 d are notshifted to the write head 63. Therefore, the plurality of magneticdomains 61 a to 61 d are less likely to be affected by magnetic fieldsof the third magnetic layer 7 a and the fourth magnetic layer 7 b.

During a write operation W/O, the plurality of magnetic domains 61 a to61 d are shifted to the write area 65. In the magnetic memory 302, thewrite area 65 is set to an area between the first electrode 4 a and asecond electrode 4 b.

In this way, the storage area 64 may be set between the read head 62 andthe first electrode 4 a. In this case, it is favorable to separate thewrite head 63 from, the storage area 64 from a perspective of retentionof information.

According to the embodiment, a magnetic memory that enables improvementof the degree of integration can be provided.

The embodiments of the present invention have been described withreference to the specific examples. However, embodiments of the presentinvention limited to the specific examples. For example, specificconfigurations of the respective elements such as the first magneticlayer 2, the conductive layer 3, the intermediate layer (insulatinglayer) 5, the second magnetic layer 6, the third magnetic layer 7 a, andthe fourth magnetic layer 7 b included in the magnetic memory can beappropriately selected from public domain by a person skilled in theart. Similar implementation of the present invention is included in thescope of the present invention as long as similar effects can beobtained.

Combinations of any two or more elements from the specific embodimentsin a technically possible range are also included in the scope of thepresent invention as long as the combinations comprise the gist of thepresent invention.

In addition, all of magnetic storage elements and non-volatile storagedevices implementable through appropriate design change by a personskilled in the art on the basis of the magnetic memories described asthe embodiments of the present invention also belong to the scope of thepresent invention as long as these elements and devices comprise thegist of the present invention.

In addition, various alternations and modifications that can beconceived by a person skilled in the art within the idea of the presentinvention are also understood to belong to the scope of the presentinvention.

Some embodiments of the present invention have been described. However,these embodiments have been presented as examples, and are not intendedto limit the scope of the invention. These new embodiments can beimplemented in various other forms, and various omissions, replacements,and changes can be made without departing from the gist of theinvention. These embodiments and its modifications are included in thescope and the gist of the invention, and are included in the inventiondescribed in claims and its equivalents.

1. A magnetic memory comprising: a structure including a first magneticlayer and a conductive layer; a second magnetic layer having the firstmagnetic layer arranged between the second magnetic layer and theconductive layer; an intermediate layer provided between the firstmagnetic layer and the second magnetic layer; a first electrodeelectrically connected with a first portion of the structure; a secondelectrode electrically connected with a second portion of the structure;a third magnetic layer provided between the second electrode and theintermediate layer; a fourth magnetic layer provided between the firstelectrode and the intermediate layer; a first semiconductor layer havinga first conductive-type, electrically connected with the firstelectrode; a second semiconductor layer having a first conductive-type,electrically connected with the second magnetic layer; and a thirdsemiconductor layer having a second conductive-type, electricallyconnected with the first semiconductor layer and the secondsemiconductor layer.
 2. The magnetic memory according to claim 1,wherein the first electrode, the intermediate layer, the secondelectrode, the third magnetic layer, and the fourth magnetic layer arelined up in a first direction.
 3. The magnetic memory according to claim1, wherein the first electrode is connected with the second electrode bya parallel circuit including a first resistor portion by the conductivelayer, and a second resistor portion by the first magnetic layer andconnected in parallel to the first resistor portion.
 4. The magneticmemory according to claim 2, wherein a resistance value of the firstresistor portion is lower than a resistance value of the second resistorportion.
 5. The magnetic memory according to claim 1, wherein theconductive layer is nonmagnetic.
 6. The magnetic memory according toclaim 1, wherein the third magnetic layer adds a magnetic field to thefirst magnetic layer.
 7. The magnetic memory according to any claim 1,further comprising: a first wiring electrically connected with thesecond magnetic layer and the second semiconductor layer; and a secondwiring electrically connected with the second electrode.
 8. The magneticmemory according to claim 7, further comprising: a circuit elementincluding the first semiconductor layer having a first conductive-typeelectrically connected with the first electrode, the secondsemiconductor layer having the first conductive-type electricallyconnected with the second magnetic layer, and the third semiconductorlayer having the second conductive-type electrically connected with thefirst semiconductor layer and the second semiconductor layer, whereinthe circuit element has a positive threshold voltage Vth and a negativethreshold voltage −Vth, and a voltage Vr between the first wiring andthe second wiring isVr<|Vth| in a read operation, and a voltage Vw between the first wiringand the second wiring isVth≦Vw or −Vw≦−Vth in a write operation.
 9. The magnetic memoryaccording to claim 8, further comprising: a first external terminal; anda second external terminal, wherein the first external terminal iselectrically connected with the first wiring, the second externalterminal is electrically connected with the second wiring, a firstpotential difference is provided to the first external terminal and thesecond external terminal in the read operation, and a second potentialdifference is provided to the first external terminal and the secondexternal terminal in the write operation.
 10. The magnetic memoryaccording to claim 1, further comprising: a third electrode electricallyconnected with a third portion of the structure.
 11. The magnetic memoryaccording to claim 10, further comprising: a third wiring electricallyconnected with the third electrode.
 12. The magnetic memory according toclaim 11, wherein first information and second information are writtenin the first magnetic layer.
 13. The magnetic memory according to claim12, wherein the first magnetic layer includes a first magnetic domainand a second magnetic domain, and the first information is written inthe first magnetic domain, and the second information is written in thesecond magnetic domain.
 14. The magnetic memory according to claim 13,wherein the first magnetic domain and the second magnetic domain areshifted in the first magnetic layer.
 15. The magnetic memory accordingto claim 14, further comprising: a third external terminal, wherein thethird external terminal is electrically connected with the third wiring,and a third potential difference is provided to the second externalterminal and the third external terminal in the shifting of the firstmagnetic domain and the second magnetic domain.
 16. The magnetic memoryaccording to claim 14, wherein the structure includes an area betweenthe first electrode and the third electrode, and the first magneticdomain and the second magnetic domain are shifted in the area of thestructure.
 17. The magnetic memory according to claim 16, wherein thearea of the structure is distant from the third magnetic layer.
 18. Amagnetic memory comprising: a structure including a first magnetic layerand a conductive layer; a second magnetic layer having the firstmagnetic layer arranged between the second magnetic layer and theconductive layer; an intermediate layer provided between the firstmagnetic layer and the second magnetic layer; a first electrodeelectrically connected with a first portion of the structure; a secondelectrode electrically connected with a second portion of the structure;a third magnetic layer provided between the second electrode and theintermediate layer; a first semiconductor layer having a firstconductive-type, electrically connected with the first electrode; asecond semiconductor layer having a first conductive-type, electricallyconnected with the second magnetic layer; and a third semiconductorlayer having a second conductive-type, electrically connected with thefirst semiconductor layer and the second semiconductor layer.
 19. Themagnetic memory according to claim 18, wherein the first electrode, theintermediate layer, the second electrode, and the third magnetic layerare lined up in a first direction.
 20. The magnetic memory according toclaim 1, wherein the third magnetic layer contains antiferromagnetism.